Motor control system



June 15, 1936- c. A. H. wATsoN ET AL 2,044,034

MOTOR CONTROL SYSTEM Filed March 2, 1954 3 Sheets-Sheet 1 June l6, 1936 c. A. H. WATSON ET Al. 2,044,034

MOTOR CONTROL SYSTEM `iled March 2, 1934 3 Sheets-Sheet 2 www@ June 16, Q A H WATSQN ET AL 2,044,034

MOTOR CONTROL SYS TEM Filed March 2, 1934 3 Sheets-Sheet 3 MMMMIMI 797s 77 Patented June 15 1936 PATENT OFFICE MOTOR CONTROL SYSTEM Charles A. H. Watson,

Highland Park, and Fred E. McKinster, Detroit, Mich., assignors to corporation of Maine McCord Radiator & Mfg. Co., Detroit, Mich., a

Application March 2.

Z Claims.

This invention relates to electrically operated driers of the type which discharge a continuous blast of heated air for hand, face, hair, apparel and other drying purposes.

An objection to devices of this character as heretofore used is that a blast of relatively cool air is discharged from the drier on each starting operation. This is dueto the fact that the blowers in these driers are operated at high speeds and at full air volume at all times and the electrical heating element for heating the air is unable to `raise the temperature of the high v'e-' locity air to the hot blast required for drying purposes until the blower has been in operation `for an appreciable length of time.

A The general purpose and object of our invention is to overcome this objection and we do so by so constructing the drier as to reduce the velocity of the air for a short period of time on starting the drier so that the heating element may rapidly raise the temperature of the low velocity air to that required for drying purposes. Thus the drying action ls not delayed as heretofore, for the initial blast is quickly brought to the temperature range of the hot blast produced by the continued operation of the blower.

To accomplish this result, we provide means in the drier assembly acting automatically on each starting of the blower to reduce the blower speed for a short period of time, say ten or twenty seconds, so that the heater may quickly raise the temperature of the slow velocity air, after which the blower is allowed to resume its normal high speed and full air supply. In practice, the motors which rotate these blowers have a top or normally high speed of approximately 3500 R. P. M. In accordance with our invention, we reduce this speed considerably on each starting operation, for example, between 500 and 1000 R. P. M. for the desired period of time to obtain rapid heating of the low velocity air.

In carrying out the objects of our invention we control the speed of the motor by providing a resistance in the motor circuit, said resistance remaining in the circuit for the period of time desired and automatically cut out after that time so that the motor may resume its normal high speed.

A further object of our invention is to control the cutting in and out of the resistance by the use o1' a timing element or mechanism automatically brought into and out of operation in the starting and stopping o1' the blower.

Other and further objects of our invention will appear from the following specification taken in 1934, Serial No. 713,660

connection with the accompanying drawings, in which:

Fig. 1v is a side view of a drier assembly embodying the features of our invention;

Fig. 2 is a top plan view of the parts shown 4 in Fig. 1;

Fig. 3 is a vertical sectional view with parts in elevation taken on line 3-3 of Fig. 2;

Fig. 4 is a perspective view with parts broken away and in section, respectively, of the actuating lever of the starting switch for the drier;

Fig. 5 is the wiring diagram; and

Fig. 6 is a front view of the drier device on a pedestal support.

Drier devices of the character to which our invention is applicable have, as shown in Figs. 1 and 2, a centrifugal blower I, an electric motor 2 for rotating the fan or air impeller 3 of the blower, and an electrical heating element 4 for heating the air discharged from the blower. These elements are usually arranged in horizontal alinement, the blower I being between the motor and the heating elements 2 and 4, respectively. The blower has an air discharge nozzle Ia extending outwardly from the front side of its casing as shown in Fig. 6. 'Ihe outer end of the nozzle is usually covered by a protective screen Ib as shown. The heating element 4 is usually located in part at least in a tubular housing 5 on the air intake side of the blower and secured to and extending laterally outward therefrom as shown in Figs. 1 a'nd 2. The outer end of this housing is open and provides the air intake opening for the blower. The heating element comprises a coil of electrical resistance wire 4a arranged in spiral form about a suitable' spider or support 4b of insulating material. The ends of the Wire are connected to terminals 6, 'I on the housing 5 whereby the heating element may be connected with the current supply in the manner to be presently described.

The supply of electric current to the motor and the heating elements 2 and 4 is controlled by a switch 8 mounted on the base plate or support 22 for the drier assembly. The switch 8 is of the double pole type having upright fixed contact posts 9, I0 arranged in pairs on opposite sides of an actuating lever having an outer member II and an inner member I2. These members straddle an upright standard I3 and the inner member I2 is pivoted intermediate its ends to the standard at I4 as shown in Fig. 3. The members II and I2 are approximately equal in length and the outer member II has its inner ends notched and engaging a fulcrum pin I5 carried at the adjacent end of the inner member I2 as shown in Fig. 4. A yoke I8 connects the main operating rod Il of the drier device with the pin I8. The rod Il is located in the pedestal support I8 for the drier and is pivoted at its lower end to a footA pedal I8 adjacent the lower end oi' the pedestal as shown in Fig. 6. In operating the drier the user presses downwardly on the pedal I8, thereby raising the rod Il and closing the switch 8 in a manner to be presently described. A spring 20 associated with the pedal raises the pedal and lowers the rod I'I to open the switch 8 when the pedal is released.

The standard I8 is secured to the base plate 2| of the switch 8. This base plate, which is of insulating material, has an opening 2Ia therein whereby the arm Ita of the yoke I8 may extend through the plate for pivotal connection with the upper end of the rod I l. The upper end of the rod Il is bent, as shown in dotted lines in Fig. l, to reach the arm of the yoke when the switch 8 is in oilset relation to the pedestal I8 as shown in the drawings. The base plate 22 for the drier assembly is also apertured t0 receive the arm of the yoke. Plate 22 in the pedestal type of device is secured to the upper end of the pedestal to support the drier assembly thereon.

The movable contacts of the switch 8 are in the form of strips or plates 28. 28 arranged on opposite sides of the actuating lever and disposed to bridge the upper ends of the contact posts 8, I8 when the switch is closed as shown in Figs. 1 and 2. These strips or plates 28 are carried by a movable support 24 in the form of a plate of insulating material, said plate being disposed above the standard I8 and pivotally connected thereto by member 28. This member is in the form of a yoke straddling the standard and is fulcrumed on the standard at 28 as shown in Fig. 3. This pivotal mounting is disposed on the outer side of the fulcrum I4 for the actuating lever and preferably slightly below the same. The contact plates 28, 28 are yieldably supported by springs 21, 2l.

'Ihe members II, I2 oi the actuating lever for the switch move in unison when opening and closing the switch 8. For ease of operation in opening the switch. the inner member I2 moves slightly in advance of the outer member II'r in the initial operation of the lever. Thereafter the members are connected together by the outer end of the member I2 engaging under a flange or ledge 28 at the outer end of the member II as shown in Fig. 4. A pair of coiled springs 28, 28 are employed for giving a quick snap opening and closing movement to the switch in its operation. These springs are located on opposite sides of the actuating lever and have their outer ends connected thereto by a pin 80. The inner ends of the springs are connected to the movable plate 24 of the switch through depending members 8 I, 8I thereon. These members may be integrally connected by being formed from a single piece of metal bent to U-form, as shown. This member is located on the plate 24 in inward spaced relation to the fulcrum I4 for the actuating lever. The parts are so constructed and arranged that the springs 28 as they pass the pivotal points I4 and 2li will impart a quick snap motion to the switch, drawing the contact plates 28, 28 into engagement with the posts 8. I8 when closing the switch and moving these plates out of contact with said posts on opening the switch.

Arranged on the base plate 22 opposite the switch 8 is a timing mechanism 82. 'Ihis mechanism comprises a pair of laterally spaced upright plates or standards 88. 88 forming a support for a speed reducing gear train of the type usually 5 employed in clock work. Secured to one terminal shaft 84 of this gear train is a disc 88 of electrical insulating material. 'I'his disc r0- tates with the shaft 84 and is provided with an arm 88 which has movement exterior of the l0 plates 88 as shown in Fig. 3. An electrical contact element in the form of a roller 8l. is mounted` on the outer end oi' the arm 88 for making contact with a pair of upright contact fingers 88, 88 secured to the base 82a of the timing 18 device. This base is of insulating material and the fingers 88 are connected in the motor circuit as hereinafter described.

Movement of the roller 8l into and out of contact with the fingers 88 is created by a pair of 20 contracting coiled springs 89, 4I) connected respectively to the opposite ends of alever 4I fulcrumed intermediate its ends at 42 on an upright standard 48 secured to the base` plate 22 of the drier assembly. Links 44, 48 connect 25 these springs with the disc 88 on opposite sides of the shaft 34 and in substantially equal radial distances therefrom. The disc has pins 48, 4l for connection with the links. the latter preferably in the form of rigid wires having their 30 ends looped about the pins as shown. The oppol site ends of the wires have a looped connection with the adjacent springs 89, 48. 'I'he lever 4I is provided with a co-planar ann 48 extending radially outward from the lever on its side op- .35 posite the springs. This arm is long enough to reach the inner end of the switch actuating lever II-I2 and engages the inner member I2 thereof in an ear 48 as shown.

When the actuating lever of the switch 8 is 40 moved to close said switch, the inner end of the A lever is moved upwardly as shown in Fig. l. This swings the lever 4I about its fulcrum 42 and moves the upper end of the lever to the right and the lower end to the left when the 45 parts are viewed as in the drawings. In this l movement the lower spring 48 is expanded and through its link 48 rotates the disc 88 in a direction to lower its contact member 8l into engagement with the fingers 88. The speed of ro- 50 tation of the disc is controlled however by the gear reduction of the timing mechanism 82 and also by a governor device 80. Ihis governor is preferably in the form of a bladed member secured to the terminal shaft 8I of the gear re- 55 duction opposite the disc 88 and its speed of rotation is controlled by the resistance oifered to the movement of its blades by contact with the surrounding air. In the device shown the speed is such that it takes approximately 10 seconds o for the arm 88 of the disc 88 to move from its uppermost position in Fig. 3 to its lowermost position in contact with the lingers 88. This time may be varied by changing the size of governor blades. The upper spring 88 of the lever 4I is fully contracted at this time and does not interfere with the downward movement of the arm.

When the actuating lever of the switch 8 is 70 moved to open the switch, the inner end of said lever is lowered, carrying therewith the arm 48 of the lever 4I as shown in Fig. 3. This rocks the lever 4I in a direction reverse to that above described, expanding the upper spring 88 and 75 rotating the disc 35 to raise its arm 33 out of contact with the ilngers 38. The speed at which the arm 36 moves upwardly is controlled by the gear reduction and its governor 50. The lower spring 40 contracts and does not interfere with this movement. A stop 52 may be provided to limit the upward movement of the arm 36 as indicated in Fig. 3. With the links 44, 45 in crossing relation, as shown, the lower'spring is connected with the upper portion of the disc 35 and the upper spring is connected with the lower portion of the disc, thereby causing rotation of the disc in opposite directions on rocking the lever 4| as described.

Arranged in the motor circuit is a resistanci 53 having a number of outlets 54 whereby the resistance desired may be obtained by connecting the wiring to the selected outlets. In the drawings, we have shown the full resistance employed in the motor circuit. The supply wires 55, 56 are connected with the terminals 9a, Illa of the forward set oi posts 9, I0 of the switch 8. Two sets of wires are connected to the terminals 9b, Illb of the rear set of posts 9, Ill. The wires 51, 58 of one set connect these terminals with the wires of the heating'element 4. As to the wires 59, 60 of the other set, the wire 59 leads directly to one of the terminals of the motor! as shown in Fig. 2. The wire 60 leads to one of the terminals 54 of the resistor 53 as shown in Fig. 2. A wire 6I connects this terminal to one of the spring contact fingers 38 as also shown in Fig. l. A wire 62 connects the other spring finger 38 to one of the other of the terminals 54 of the resistance 53 and this terminal by a wire 63 is connected to the other terminal of the motor 2.

The wiring diagram is illustrated in Fig. 5. By referring to this diagram, it will be clear that when the switch 8 is closed and the contact member 31 of the timing mechanism is out of engagement with the iingers 38, the iiow of current to the motor will be through the resistance 53. Thus the speed of the motor will be reduced and the amount or volume of air drawn into the blower will be less than when the motor is operating at full current supply. When the contact 31 is moved into engagement with the fingers 38, the resistance in the motor circuit will be cut out and the motor will operate it at full or normally high speed. The heating element 4 receives its full current supply whether the resistance is in or out of the motor circuit. 'I'his is due to the fact that the heating element is connected with the current supply in advance of the switch 31-38.

The operation of the mechanism shown and described has already been given in connection with the description of the various parts of the mechanism. It will be unnecessary therefore to again describe the operation in detail. Briefly, with the resistance 53 in the motor circuit on starting the drier, the speed of rotation of the motor will be reduced and the amount of air drawn into the blower will be less than when the blower is operated at its full or normal high speed. At the reduced air supply, the heating element 4 may quickly raise the temperature oi' the low velocity air so that a hot blast will be discharged from the blower almost immediately on starting it or within a very short time thereafter. This time element is controlled by the timing device 32 and as heretofore stated, closes the switch 31-38 within approximately ten seconds after the motor has been started. By this time a hot blast is being discharged from the blower, and the motor is rotated at its normal high speed by cutting the resistance 53 out of the motor current." The foot pedal I9 must be held depressed to keep the blower in operation. On releasing the pedal, both switches are opened and the timing mechanism 32 is automatically restored to its starting position to place the resistance 53 in the motor circuit. The resistance 10 used will be of the type whereby the motor speed may be reduced to the speed desired, as Within the example heretofore given.

'Ihe disc 35 may be given irregular shape, as shown in the drawings, to avoid interference with 15 the adjacent shaft in the gear train. The drier assembly is housed within a cover 64 at the upper end of the pedestal I8. 'Ihe discharge nozzle la of the blower extends outwardly through a vertical slot in this cover, the blower 20 being adjustable above the axis of the motor for raisingand lowering the nozzle to suit the' convenience of the user of the device.

The details of construction and arrangement of parts shown and described may be variously 25 changed and modified without departing from the spirit and scope of our invention except as pointed out in the appended claims.

It is to be understood that we do not limit ourselves to the particular form of switch disclosed for actuating the device for controlling the speed of the motor as said device may be operated by other mechanical means, such as a control push rod. Moreover, it is within the contemplation of our invention to vary the period of the timing action of the said motor control device by employing springs of different tensions or adjustable means for the springs or the links for adjusting the spring tension.

We claim as our invention:

1. In combination, an electric motor, a circuit for the motor, a main switch and a resistance in the motor circuit for respectively starting and stopping the motor and reducing the speed o! rotation thereof, a shunt circuit for the resistance, a supplemental switch in the shunt circuit for cutting the resistance in and out of the motor circuit, a timing device for retarding the opening and closing of the supplemental switch, said supplemental switch having separable contacts, one in the shunt circuit and the other carried by a revoluble member in the timing device, a lever pivoted intermediate its ends and connected with the main switch for actuation thereby, and 55 means including tension springs connecting the opposite ends of the lever with the revoluble member for opening and closing the supplemental switch in response to the opening and closing movement of the main switch. 60

2. In combination, an electric motor, a circuit for the motor, a main switch and a resistance in the motor circuit for respectively starting and stopping the motor and reducing the speed of rotation thereof, a shunt circuit for 65 the resistance, a supplemental switch in the shunt circuit for cutting the resistance in and out of the motor circuit, a timing device for retarding the opening and closing of the supplemental switch, said supplemental switch having separable contacts, one in the shunt circuit and the other carried by a revoluble element in the timing device, a lever fulcrumed between the timing device and the main switch and having a pair of arms movable in union and arranged in right angular reletion to each other, one erm of seid lever extending towsrd the msin switch and connected therewith for ectustion thereby in opening and closing seid main switch. the other um o! the lever extending on opposite sides of the first mentioned stm, end linksnmnged in crossing reistion end connecting the opposite ends ot the second mentioned um with the rot'etoble element of the timing device on Opposite l sides 0i' its axis 0f rotation. id links includinl directions by the main switch to elect rotation 'I of the revolubie element.

CHARLES A. H. WATSON. ml) E. HCKINBTER. 

